The
canonical correlation analysis (CCA) forecast of SST in the central Pacific
(Barnett et al. 1988, Science, 241, 192‑196; Barnston and
Ropelewski 1992, J. Climate, 5, 1316‑1345), is shown in Figs.
F1 and F2. This forecast
is produced routinely by the Prediction Branch of the
Climate
Prediction
Center
. The predictions from the National Centers for
Environmental Prediction (NCEP) Coupled Forecast System Model (CFS03) are
presented in Figs. F3 and F4a,
F4b.Predictions
from the Markov model (Xue, et al. 2000: J. Climate, 13,
849‑871) are shown in Figs. F5 and F6.Predictions from the latest version of the LDEO model (Chen et al.
2000: Geophys. Res. Let., 27, 2585‑2587) are shown in Figs.
F7 and F8.Predictions using linear inverse modeling (Penland and Magorian 1993:
J. Climate, 6, 1067‑1076) are shown in Figs. F9
and F10. Predictions from the Scripps / Max
Planck Institute (MPI) hybrid coupled model (Barnett et al. 1993: J.
Climate, 6, 1545‑1566) are shown in Fig. F11.Predictions from the ENSO‑CLIPER statistical model (Knaff and
Landsea 1997, Wea. Forecasting, 12, 633‑652) are shown in
Fig. F12.Niño 3.4 predictions are summarized in Fig. F13,
provided by the Forecasting and Prediction Research Group of the IRI.

The CPC and
the contributors to the Forecast Forum caution potential users of this
predictive information that they can expect only modest skill.

Outlook

A transition from ENSO-neutral
to La Niña conditions is possible during the next 2-3 months.

Discussion

The pattern of anomalous sea surface
temperatures (SSTs) during April 2007 was consistent with ENSO-neutral
conditions in the tropical Pacific, with average to below-average SSTs
extending from the date line to the west coast of South America (Fig. T18). The
latest SST departures are slightly positive in the Niño 4 and Niño 3.4
regions, slightly negative in the Niño 3 region and negative in the Niño
1+2 region (Table T2).An area of
anomalously warm SSTs persisted well west of the date line (near 150ºE) (Fig.
T18).

The
equatorial upper-ocean heat content (average temperature departures in the
upper 300 m of the ocean) remained below-average across the central and
east-central equatorial Pacific, with temperatures at thermocline depth
generally 2°-4°C below average (Fig. T17).Consistent with the surface and sub-surface temperature patterns,
stronger than-average low-level easterly winds persisted over the central
equatorial Pacific (Figs. T7
and T20),
and convection was enhanced over the western equatorial Pacific and
suppressed east of the date line (Fig.
T25). Collectively, these atmospheric and oceanic conditions
continue to reflect an evolution toward a Pacific cold (La Niña) episode.

The value of the Oceanic Niño Index (ONI;
3-month running mean average of SST anomalies in the Niño 3.4 region –
computed using the Extended Reconstructed SST version-2 data set) for
February – April 2007 is +0.1°C, which reflects ENSO-neutral conditions in
the tropical Pacific. Most
of the statistical and coupled model forecasts, including those from the NCEP
Climate Forecast System (CFS), indicate below-average SSTs in the tropical
central and eastern Pacific during the next several months (Figs. F1,
F2, F3, F4a,
F4b, F5, F6,
F7, F8, F9,
F10, F11, F12
and F13). Some forecast models, including the CFS, indicate a transition to
La Niña during May-July 2007. These forecasts are consistent with the observed evolution
in atmospheric and oceanic conditions towards a Pacific cold episode.
However, the spread of the most recent statistical and coupled model
forecasts (ENSO-neutral to La Niña) indicates considerable uncertainty as to
exactly when La Niña might develop and how strong it might be.

Weekly
updates of SST, 850-hPa wind, OLR and features of the equatorial subsurface
thermal structure are available on the ClimatePredictionCenterhomepage at: